The Logitech G900 Chaos Spectrum is one of the finest goddamn mice I've had the pleasure of using.
One of the my issues with some hardware built for gaming is the tendency to overdesign. Adding hard edges, brighter colors, more buttons, more features, more everything. My previous workhorse mouse is a Logitech G502 Proteus Spectrum, purchased on my own dime because it was one of the current best on the market. The G502 is overdesigned along the inner edge of the mouse, a pile of sharp edges, buttons, and lights. You can feel everything jutting out.
With the G900, Logitech is restrained. In its default setup, you have left and right mouse buttons, two thumb buttons, a scroll wheel, a wheel adjustment switch, two DPI buttons, and another switch on the bottom to change mouse profiles. The simplicity is clear and the only hallmark of overdesign for gaming is the gulf between the buttons and the rear of the mouse. You won't feel that during most situations, though I find my finger tracing the gulf when I'm not actively using the mouse. The mouse is made of plastic, but it has a sturdy, solid feel to it. No flex at all.
The G900 is an incredibly light mouse, coming in at 107g; if you want something heavier, you'll need to find another mouse, because there's no adjustable weights here like there are in the G502. This was tuned for professional-level players, who want something that's an extension of their hand. The G900 sacrifices where it needs to, like dropping the solid scroll wheel for a lighter, spoked metal version.
Where the G900 allows adjustments is in the number of buttons. This is an ambidextrous mouse, perfectly symmetrical, except for its adjustable thumb buttons. It comes configured with two thumb buttons on the left side for right-handed use, but you can swap those out with similar buttons for the right side.
Your options include either the left side thumb buttons, right side thumb buttons, or both. The mouse comes with a solid plate for whichever side you aren't using. The buttons themselves are easy to remove since they're attached to the G900 with magnets. While the "magnets" part may give you pause, I haven't had any issues with the buttons falling off during use or basic click activation.
Logitech has also rethought the primary mouse buttons, probably aiming at replicating the satisfying click of a mechanical keyboard. The left and right mouse buttons are attached to a metal pivot bar. There's a good amount of travel to them no matter where you press and activation always ends in that solid "click". I jam with it.
The G900 is one of the few pro-level mice that has a wireless option. There are three ways to attach the mouse to your desktop or laptop. You can use the 6 foot cloth-braided charging cable to keep the G900 attached to your computer at all times, attach the tiny receiver directly to your PC, or you can attach the receiver - which comes in a case with the additional button caps - to a weight and the braided cable for alternative placement. The first two options are better for normal, close quarters gaming setups, while the latter is better for couch PC gaming.
Regardless of which method you use, the Logitech G900 remains responsive. The mouse is accurate as hell when it comes to the sensor; Logitech's PMW3366 optical sensor can track anywhere from 200 to 12,000 DPI. That accuracy comes across in wired or wireless modes, with no noticeable jitter or acceleration. Every click comes across wonderfully, since the mouse has a 1ms polling rate whether you're wired or wireless.
In wireless mode, you do have to worry about battery life, but on a single charge, the Logitech G900 runs just under 30 hours for me. That's right within Logitech's 24-32 hour stated battery life range. You can probably juice that up a bit by turning off the RGB-lit G logo on the mouse, but I didn't find that to made a big difference. The mouse itself goes into sleep mode after 30 minutes of unuse, but it wakes up really quick. All told, you're talking about a once-a-week charge if you're on the computer as much as I am.
In play and work, the Logitech G900 is a dream of a mouse. It's simply great right out of the box and I got used to the feel of it rather quickly. The major drawback of the G900 is price. This engineered marvel will set you back $150, which is a bit pricey for a gaming mouse. I think the package is worth that, but I understand if some don't want to spend that much. (Thanks to the magic of Black Friday, the G900 is $110 on Amazon and NewEgg. I'd get on that while the price is low.)
Regardless of price, I'll simply restate the opening of this review: The Logitech G900 Chaos Spectrum is one of the finest goddamn mice I've had the pleasure of using. You simply have to decide how much that is worth to you.